The invention is directed to a method of treating seeds using non-aqueous solvents and to the formulations used in the treatment.
Seed treatment is a growing niche within the general area of crop protection. Two main factors have contributed to this. First, the technology of building crop protection and/or specific attributes into the genetic makeup of the plant has led to a significant increase in the cost of the seed. Second, seed exposure has increased because it is being planted earlier into cold, often hostile, no-till soils that provide a refuge for soil-borne diseases and insects.
It is generally known to coat seeds for various purposes, including seed identification, increasing the storage life of the seed, aiding in seed delivery to the field, increasing the viability of the seed and/or the resultant plant in the field (e.g., xe2x80x9cweed and feedxe2x80x9d scenarios), and various other purposes. The coatings will include, for instance, fungicides, insecticides, growth hormones, and other seed treating ingredients. The recent development of transgenic crops has resulted in an increased focus on seed treatment, because of the increased value of such genetically-altered seeds.
Seed treatments are traditionally applied as aqueous dispersions or water-based flowable formulations of the active ingredients. However, aqueous treatment methods have several disadvantages. Among these are: (1) not all seed protectant chemicals are soluble and/or stable in water, thus limiting the type of treatments available; (2) water soluble protectants rapidly leach off and away from the seed, thus diminishing effectiveness of the treatment; (3) aqueous dispersions do not cover the seed uniformly and can be physically removed by abrasion and attrition; and (4) a drying step is required to prevent premature germination due to the presence of water. Historically, alternatives to aqueous-based treatment methods have been disfavored because alternative solvents, mainly organic solvents, were believed to be toxic toward seeds (phytotoxic).
There are reports in the literature that the OSIT method (Organic Solvent Infusion Technique) may be useful in the germination of hard coated seeds. In this method, the seed is soaked in the solvent for a fixed amount of time. The solvents are generally highly volatile solvents such as xylene, acetone, methylene chloride, and the like, which have boiling points between about 40 and 150xc2x0 C. This technique has been studied in the context of translocation experiments, but has yet to be proven successful and is not commercially viable using typical commercial equipment.
In U.S. Pat. No. 5,849,320, an insecticidal coating for a seed is described comprising polymer binders. The polymer serves as a matrix for the insecticide and is intended to remain on the seed as a coating. The problem solved by this patent is described therein as the xe2x80x9cphototoxic effect of the insecticide on the seed.xe2x80x9d
Accordingly, there still remains a need for a generalized, commercially viable method of delivering all sorts of seed treatments, that will solve the aforementioned drawbacks of aqueous treatment methods while having minimal or no negative effects on the seed.
The present inventor has surprisingly found that certain non-aqueous solvents for seed coating display minimal or no phytotoxic effects toward seeds (i.e., the formulations will be xe2x80x9cphytoblandxe2x80x9d). Seeds such as corn, cotton, wheat, soybean and rice, among others, may be treated with certain non-aqueous solvents, such as hydrocarbon solvents (e.g., normal paraffinic, isoparaffinic, dearomatized mixed aliphatics and aromatics) and heteroatom-substituted hydrocarbon solvents (e.g., aliphatic esters), with little or no negative effects seen from the use of non-aqueous solvents. In certain cases the solvent alone appears to enhance germination over untreated seeds. The present invention allows for the delivery of seed treatment agents, such as protectant chemicals (fungicides, insecticides, growth hormones, and the like) which are more readily soluble in organic solvents, provides for more uniform coverage of the seeds, less likelihood that the treatment agent will leach out from the seed, thus providing for longer protection and often the use of less active ingredient. Furthermore, with the use of non-aqueous solvents, no separate drying step is needed. The preferred solvents used according to the present invention have boiling points above 150xc2x0 C. and more preferably from about 160 to 280xc2x0 C.
As used herein, the term xe2x80x9cseed treatment agentsxe2x80x9d (or xe2x80x9cseed-treating agentsxe2x80x9d) will refer to the solute which is dissolved by the non-aqueous solvent and coated on the seed. Seed treatment agents other than those known in the art as xe2x80x9cprotectantsxe2x80x9d may also be incorporated and coated on the seed using the non-aqueous solvents according to the present invention. Such ingredients, generally considered to be biologically inert, include but are not limited to colorants to aid in seed identification, dust control agents, flow aids to aid in seed delivery, and the like. These seed treatment agents will be referred to herein generally as xe2x80x9cinert ingredientsxe2x80x9d. The term xe2x80x9cactive ingredientxe2x80x9d as used herein will refer to those seed treatment agents generally considered to be biologically active, such as the protectants listed above. Furthermore, as used herein, the term xe2x80x9csolventxe2x80x9d refers to that category of chemicals which are liquid under ambient conditions and provide the specific function of solvating a substance and then ultimately evaporating. The term xe2x80x9cfluidxe2x80x9d is used interchangeable with xe2x80x9csolventxe2x80x9d below.
Another unexpected finding of the present inventors is that non-aqueous solvent formulations can provide for systemic treatment of the seed, since the waxy seed coating is more readily penetrated by such solvents than water.
A further surprising discovery is that non-aqueous solvents have been found to improve germination of hard coated seeds.
Yet another advantage of the present invention is that it allows the use of common commercial treatment equipment while affording superior results.
Thus, it is an object of the present invention to provide for a non-aqueous solvent system for seed treatment methods.
It is a further object of the invention to improve seed performance by providing for a wider variety of active and inert ingredients to be coated onto the seed.
Yet another object is to provide for systemic treatment of seed by providing a delivery system that is more readily translocated through the seed coat.
Still another object is to provide a method wherein less active ingredient is required in the formulation and/or fewer applications of the formulation onto the seed is required.
Yet still another object of the invention is to provide a method of seed treatment, and formulation used therein, providing for increased level of protection for seeds planted under reduced or conservation tillage.